I. If x−y=xy=1−x−y, then x+y is 56 II. The system of equations 3x+2y=a and 5x+by=4 has infinitely many solutions for x and y, then a=4,b=3 Which is true?
A
I only
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B
II only
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C
Both I and II
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D
None of these
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Solution
The correct option is A I only StatementA−Givenx−y=xy−−−(1)1−x−y=xy−−−(2)andx−y=1−x−y−−−(3)⇒x−y+x+y=1⇒2x=1⇒x=12−−−(4)Substitutingx=12in(1)weget12−y=12y⇒y=13−−−(5)Adding(4)and(5)wegetx+y=12+13=56So,thisstatementistrue.StatementB−Wehave3x+2y=aand5x+by=4.Puttinga=4andb=3weget5x+3y=4and3x+2y=4Weseethatcoefficientofxandyintheequationsaredifferent.So,thesystemisconsistentandtheydonothaveinfinitesolution.So,statementBisnottrue.StatementD−ItisobviouslyincorrectasstatementAiscorrect.